The present invention relates to a gate valve for isolating an atmosphere gas in a chamber of a vacuum treatment apparatus for treating objects, such as liquid crystal substrates (LCD substrates), semiconductor wafers, etc., from the outside.
In a conventional etching apparatus, for example, to-be-treated objects such as LCD substrates are set in a cassette chamber. These objects are taken out one after another from the cassette chamber and loaded into a load-lock chamber, which adjoins the cassette chamber, by means of a transportation unit in the load-lock chamber. When the LCD substrates are thus loaded into the load-lock chamber, an atmosphere gas in this chamber is set at negative pressure. Thereafter, the substrates are transported from the negative-pressure chamber into a treatment chamber by means of the transportation unit. According to this transportation method, however, the load-lock chamber is set at negative pressure every time one of the LCD substrates is taken out from the cassette chamber, so that the transportation time is very long.
FIGS. 6 to 10 show an example of an etching apparatus that facilitates reduction of the transportation time. In this apparatus, a plurality of untreated LCD substrates are collectively stored in a buffer mechanism in the load-lock chamber. The substrates in the buffer mechanism are taken out one after another and transported into a treatment chamber to be treated therein. The treated substrates are returned to an original position in the buffer mechanism. Since the LCD substrates are not transported one by one between the cassette chamber and the load-lock chamber, the total transportation time is shortened for it. This etching apparatus will now be described in detail with reference to the accompanying drawings.
As shown in FIGS. 6 and 7, the etching apparatus comprises first and second chambers 1a and 1b for etching the objects and a load-lock chamber 3 that is airtightly connected to the chambers 1a and 1b through an open-close mechanism 2. The mechanism 2 is opened or closed when pressures in the chambers 1a, 1b and 3 are adjusted to negative values, individually. The load-lock chamber 3 contains a transportation mechanism 6, which includes a transportation arm 5 for transporting an object 4 to be treated to a predetermined position, a buffer mechanism (not shown) for temporarily holding the object 4 to be transported. Since the chambers 1a and 1b have the same construction, only the first chamber 1a will be described below.
As shown in FIGS. 7 to 10, the first chamber 1a has a chamber body 7 having a profile in the form of a rectangular box. The front face of the chamber body 7 is provided with a rectangular aperture 8 and an O-ring 8a surrounding the same. The aperture 8 is opened or closed by means of a gate valve that is attached to the chamber body 7 for operation. The gate valve includes a mounting plate 9 that is attached to the left-hand side portion of the chamber body 7. The plate 9 vertically extends so that its lower end portion extends downward beyond the lower part of the chamber body 7. A vertically extending linear guide 10 is fixed to the mounting plate 9. Behind the guide 10, an air cylinder 11, which constitutes a lift mechanism, is fixed to the mounting plate 9. In this case, the air cylinder 11 is directed plumb so that its expansion rod 12 can extend or contract in the vertical direction. A bracket 14 is fixed to the distal end portion of the rod 12 by means of a free joint 13 so as to project forward in the horizontal direction. Fixed to the front end portion of the bracket 14 is a coupling member 15, which extends vertically upward. A linear block 16, which is slidably attached to the linear guide 10, is fixed to the upper end portion of the member 15 by means of a plurality of bolts 17.
The proximal end portion of a valve plate supporting member 18, having the form of a rectangular plate, is fixed to a side face of the linear block 16 by means of a plurality of bolts 19. The distal end portion of the member 18 extends toward the front face of the chamber body 7. Thus, the valve plate supporting member 18 is supported like a cantilever on the linear block 16.
A valve plate 21 for opening and closing the aperture 8 of the chamber body 7 is supported on the valve plate supporting member 18 by means of a plurality of link mechanisms 20. The link mechanisms 20 are arranged individually in one position at the upper part of the supporting member 18 and two positions at the lower part of the member 18. As shown in detail in FIG. 10, each link mechanism 20 is composed of a link receiver 22b attached to the supporting member 18, a link receiver 22a attached to that part of the valve plate 21 which corresponds to the receiver 22b, and a link 24 having its opposite end portions rockably coupled to the receivers 22a and 22b by means of pivot pins 23a and 23b, respectively. As shown in FIG. 8, lugs 25 protrude sideways from the opposite side portions of the lower end of the valve plate 21, individually. Roller stoppers 26, which can engage their corresponding lugs 25, are provided individually on the opposite side portions of the lower end of the chamber body 7 that face the lugs 25.
As the expansion rod 12 of the air cylinder 11 is extended or contracted, in this arrangement, the linear block 16 is vertically slid along the linear guide 10 by means of the bracket 14 and the coupling member 15. Accordingly, the valve plate supporting member 18, which is fixed to the block 16, and the valve plate 21, which is supported by the member 18, also move vertically. When the supporting member 18 ascends together with the valve plate 21 so that the plate 21 faces the aperture 8 of the chamber body 7, the lugs 25 engage their corresponding stoppers 26. When the supporting member 18 further ascends in this state, the link 24 of each link mechanism 20 rocks around the pivot pins 23a and 23b, since the valve plate 21 is restrained from ascending by the lugs 25 and the stoppers 26 in engagement with one another. Guided by the roller stoppers 26, moreover, the valve plate 21 moves away from the valve plate supporting member 18. As this is done, the valve plate 21 is pressed against the O-ring 8a on the front face of the chamber body 7, so that the aperture 8 is hermetically closed by the plate 21. When the valve plate supporting member 18 is lowered as the air cylinder 11 operates with the aperture 8 closed by the valve plate 21, the lugs 25 are disengaged from their corresponding roller stoppers 26, and the link 24 of each link mechanism 20 is rocked. At the same time, the valve plate 21 descends away from the front face of the chamber body 7, so that the aperture 8 of the body 7 is opened.
The inside of the valve plate 21, which faces the interior of the chamber body 7, can be contaminated by gases and the like in the body 7. Accordingly, the inside of the plate 21 must be cleaned at regular intervals. The valve plate 21 can be cleaned when the aperture 8, e.g., that of the first chamber 1a on the left-hand side of FIG. 7, is opened so that the plate 21 is situated under the front face of the chamber body 7. However, a drive unit for an elevator mechanism (not shown) in the chamber body 7 is located in the lower part of the body 7, and makes it difficult to clean the inside of the valve plate 21. In cleaning the inside of the plate 21, therefore, an operator is expected to make a reach for the rear side of the chamber body 7 from the front side. In this state, however, the operator cannot access all the corners of the inside of the valve plate 21, and therefore, cannot clean it thoroughly. Before starting the cleaning, therefore, the operator loosens the bolts 19, which couple the linear block 16 and the valve plate supporting member 18, and removes the valve plate 21 together with member 18 from the chamber body 7. Since the member 18 and the plate 21 are weighty, it is hard and dangerous for one operator to support and clean them.